It is believed that there are presently about 200,000 patients with chronic renal failure in Japan. Of them, 92% to 93% receive hemodialysis as a maintenance treatment while the remaining 7% to 8% receive peritoneal dialysis.
“Dialysis” here means a process of removal of certain molecules from body fluid due to a concentration gradient by filtering it across a membrane, making use of different molecular weights. Thus, this process assists impaired renal function of the patients by dissolving various substances which are accumulated in the body through metabolic activities—solutes (such as urea (U) as a uremic toxin and creatinine (Cr)), electrolytes (Ca2+, Cl−, Na+, and K+), excess water and the like—out of the body fluid into a dialysis solution, and by then discharging the dialysis solution from the body as drained fluid. Two distinguished methods used for dialysis are hemodialysis (HD) and peritoneal dialysis (PD). Hemodialysis is a mechanical blood purification procedure to pass blood through the extracorporeal circulation, while peritoneal dialysis is a blood purification procedure achieved by infusing a dialysis solution into the peritoneal cavity and filtering blood through the peritoneum. Conventionally, either one of the dialysis procedures has been applied to the patients. In the case when deficient renal function cannot be fully compensated, it is considered as desirable to perform extracorporeal dialysis treatment using hemodialysis.
With peritoneal dialysis, the patients perform dialysis treatment mainly at home. The home dialysis involves the repetition of the following steps several times a day: introduction of a dialysis solution into the peritoneal cavity performed by patients themselves using a catheter; retention of the introduced dialysis solution for several hours; and then drainage of the dialysis solution. The patient record the amount of excess water drained from the body (referred to as the “volume of water removal”) every time when a dialysis solution is drained, and submits the records to doctors in a subsequent medical examination to obtain a prescription. Such a peritoneal dialysis procedure is called CAPD (Continuous Ambulatory Peritoneal Dialysis). Doctors take particular note of the volume of water removal of the patients, and choose appropriate prescriptions for the patients based on the volume of the drained water.
A peritoneal dialysis system in which a condition of patient's peritoneal function is simulated by a computer has been developed in recent years (see Japanese Laid-Open Patent Application Publication No. 2000-140100). This peritoneal dialysis system enables testing aspects of peritoneal function, such as the rates of solute removal and transperitoneal water removal, by computing Pyle-Popovich's mathematical model, known as a macroscopic model of peritoneal dialysis, from patient's data—the concentration of each solute, the volume of water removal and so on included—obtained by using PET (Peritoneal Equilibration Test, 1987). In general, a commercially available personal computer is typically employed in an apparatus operating such a system.
The above-mentioned peritoneal dialysis system is, however, generally capable of only making a diagnosis either qualitatively or quantitatively, although it can assess peritoneal function of a patient at the time when data is collected, based on the concentration of each solute and the volume of water removal. Accordingly, it is very difficult to study future changes in patient's peritoneal function (so-called “a mechanism of deterioration in peritoneal permeability) by using such a system.
For example, as to data obtained from a patient, in the case when an apparent volume of water removal indicated by a numerical value of the data is low, the following can be considered as possible causes. However, it is impossible to determine which one of those is the actual cause.
A: water is not drained out since the catheter tip inserted into the peritoneum is physically blocked or malpositioned (external factor);
B: the lymphatic system of the peritoneum has an elevated level of reabsorption capability; and
C: actual peritoneal function (the rate of transperitoneal water removal) has been reduced.
Of them, when A is the real cause, the blockage in the catheter is removed or the position is corrected, while anti-inflammatory agents are administered into the lymphatic system when B is the cause. If the cause is C, dialysis modality is switched from peritoneal dialysis to hemodialysis. Thus, the ways of handling the situation are much different depending on the real cause. In addition, when both B and Care the causes, the patient may possibly have complications with peritonitis or encapsulated peritoneal sclerosis, and therefore much consideration has to be given to how to treat the patient. Thus, conventional methods of testing peritoneal function do not fully allow critical judgments to be made to determine appropriate treatments for patients, and therefore, there is still room for improvement.
The present invention has been made in view of the above problems, and aims at offering a method for testing peritoneal function and a peritoneal dialysis planning apparatus which allow (i) to accurately analyze peritoneal function (a mechanism of deterioration in peritoneal permeability) of patients with peritoneal dialysis by using various types of data obtained through conventional methods and (ii) to apply the results of the analysis to future diagnostic prescriptions.